The full impact of the blast from Supernova 1987A has been revealed in images from Nasa's Chandra X-ray space telescope.

The observations are the first time that X-rays from a shock wave have been imaged at such an early stage of an exploding star.

They reveal a violent scene in which matter is battered to temperatures of 10 million degrees Celsius.

Supernova 1987A (SN 1987A) was seen to blow up on 24 February 1987. It was the first bright supernova seen from Earth for 400 years and has given astronomers a unique opportunity to test their theories of supernovae.

Hubble double

SN 1987A was also observed recently with the Hubble Space Telescope which showed gradually brightening hot spots from a ring of matter ejected by the star thousands of years before it exploded.

Chandra's X-ray images show the cause for this brightening ring. A shock wave is smashing into portions of the ring at a speed of 4,500 kilometres per second (10 million miles per hour).

Chandra was launched in July 1999

The gas behind the shock wave has a temperature of about 10 million deg C, and is visible only with an X-ray telescope.

"With Hubble we heard the whistle from the oncoming train. Now, with Chandra, we can see the train," said David Burrows of Pennsylvania State University, leader of the science team analysing the Chandra data on SN 1987A.

Model explosion

The X-ray observations appear to confirm the general outlines of a model developed by team member Richard McCray of the University of Colorado, Boulder, and others.

This suggests that a shock wave has been moving out ahead of the debris expelled by the explosion.

As this shock wave collides with material outside the ring, it heats it to
millions of degrees.

"We are witnessing the birth of a supernova remnant for the first time," said Dr McCray.

Bright future

The Chandra images clearly show the previously unseen, shock-heated matter just inside the optical ring.

Comparison of the Chandra observations, made in October 1999 and January 2000, and the Hubble observations (February 2000), show that the shock wave is just beginning to hit the ring.

In the next few years, the shock wave will light up still more material in the ring, and a reverse, inward moving, shock wave will heat the material ejected in the
explosion itself.

"The supernova is digging up its own past," said Dr McCray.

SN 1987A was a blue supergiant star, 20 times the mass of our Sun. It is 163,000 light years from Earth in the Large Magelllenic Cloud.